Project Abstract The TTR Amyloidoses (ATTRs) are rare progressive fatal diseases that affect multiple organs, causing a wide range of debilitating clinical symptoms. ATTRs are caused by the misfolding/aggregation and deposition of transthyretin (TTR) aggregates with subsequent tissue compromise. Over 100 germ line mutations are associated with autosomal dominant ATTRs, with varying penetrance and clinical manifestations even in individuals with the same mutation. ATTR presenting as primary polyneuropathy (FAP) or cardiomyopathy (FAC) are traditionally diagnosed through clinical observations, Congo red and immunohistochemical staining of tissue biopsies, with the diagnosis confirmed by genetic testing. Even with emerging technology such as PET amyloid imaging, lack of accessibility and lack of specificity are still factors making ATTRs widely underdiagnosed diseases. Recent advances in the development and commercialization of disease modifying therapeutics targeting ATTRs further underline the need for early and specific diagnosis. It is clear that early detection and treatment of the TTR amyloidoses and other amyloid diseases, notably light chain amyloidosis, lead to a superior clinical outcome. In addition to early diagnosis and patient identification, drug development programs targeting ATTRs will greatly benefit from incorporating an objective biomarker that can monitor drug response or serve as a validated surrogate endpoint for regulatory agency assessment. Misfolding and aggregation of mutant TTR presumably occurs from the time of conception and continues for years before amyloid formation is detected and symptoms emerge. These distinctive non-native protein structures are believed to be the proximal pathogenetic molecules producing tissue damage. Reduction of the pathologically related species is a necessary step in achieving a favorable clinical outcome, regardless of therapeutic modality. Hence these non-native protein structures are ideal biomarkers for early patient identification, and as indicators of response to treatment. We have developed an immunoassay (NNTTR-Dx) using proprietary antibodies specific for misfolded forms of TTR. We have shown that the NNTTR-Dx assay can rapidly and accurately identify V30M and other ATTR polyneuropathy patients. It has also been used to demonstrate quantitative reduction of non-native forms of TTR in plasma samples of patients receiving different classes of ATTR therapeutics. Herein, we propose to further develop the antibodies/assay and to cover additional ATTR mutations associated with other disease phenotypes. A successful outcome of this proposal will be a rapid diagnostic test that can specifically identify all ATTR patients and monitor their response to therapeutics. If we are successful, further development will be pursued in a phase II SBIR proposal.